1. Field of Invention
The present invention relates to a method of forming dual damascene structure. More particularly, the present invention relates to a method of forming dual damascene structure that has a greater ohmic contact area.
2. Description of Related Art
FIGS. 1A through 1D are cross-sectional views showing the progression of manufacturing steps in forming a dual damascene structure according to a conventional method. First, a patterned conductive layer 102 is formed in a substrate 100 having certain device structures (not drawn) formed thereon as shown in FIG. 1A. Next, an oxide layer 104 and a silicon nitride layer 106 are sequentially formed over the substrate 100.
Thereafter, as shown in FIG. 1B, photolithographic and etching techniques are used to pattern the silicon nitride layer 106 to form an opening. Subsequently, an insulating layer 108 is formed over the substrate 100. Then, using a patterned photoresist layer (not drawn) as a mask, the insulating layer 108 is anisotropically etched in a dry etching operation to form an insulating layer 108a. In the meantime, using the silicon nitride layer 106a as a mask, the oxide layer 104 is also etched until the conductive layer 102 is exposed.
Consequently, a trench 110a is formed in the oxide layer 104a and the insulating layer 108a as shown in FIG. 1C. Thereafter, a glue layer 112 is formed over the insulating layer 108a and the oxide layer 104a on the interior surface of trench 110a. Later, the trench 110a is completely filled by a metal to form a metallic layer 114. Finally, a chemical-mechanical polishing (CMP) method is used to remove portions of the metallic layer 114 lying above the insulating layer 108a, thereby forming a metal plug 114a and a conductive line 114b as shown in FIG. 1D.
For a conventional dual damascene structure, its conductive layer 102 and its metal plug 114a have a two-dimensional contact area. As the line width of semiconductor devices continues to shrink, contact area provided by the aforementioned method will shrink as well. Hence, resistance of the ohmic contact will continue to increase, thus affecting reliability of the integrated circuit devices.
In light of the foregoing, there is a need to improve the method of forming dual damascene structure.